1. Field of the Invention
The present invention relates to a sanitary napkin suitable for nighttime use. More particularly, the invention relates to a sanitary napkin provided with rear flaps for widely covering a posterior part of the crotch and the buttocks.
2. Description of the Related Art
For nighttime use, there have been known elongated sanitary napkins with fold-back flaps in its front portion and rear flaps in its rear portion.
FIG. 8 is a top plan view showing a conventional sanitary napkin 101 of this type with its skin-side surface directed upward.
The sanitary napkin 101 has a main body constructed to include: a liquid-permeable topsheet located on the skin-side surface; a liquid-impermeable backsheet located on the garment-side surface; and a liquid absorbent layer disposed between the topsheet and the backsheet. The main body has a front portion with fold-back flaps 102, 102 projecting from transversely opposing sides thereof and a rear portion with rear flaps 103, 103 projecting from the transversely opposing sides. The sanitary napkin 101 is intended to be placed on an inner surface of an undergarment from a crotch part to a back body and fixed to the inner surface of the undergarment through a pressure-sensitive adhesive layer disposed on a garment-side surface of the backsheet.
The fold-back flaps 102, 102 may be folded back to cover either side edge of the crotch part of the undergarment and adhered to an outer surface of the crotch part through pressure-sensitive adhesive layers. The rear flaps 103, 103 may be placed on the undergarment in an unfolded state to extend from a rear portion of the crotch part to the back body, wherein the garment-side surfaces of the rear flaps 103, 103 can be fixed to the inner surface of the undergarment through pressure-sensitive adhesive layers.
On the skin-side surface of the main body, leakage preventing walls 104, 104 are provided to extend longitudinally on each side of a longitudinal centerline Oy-Oy. Each leakage preventing wall 104 is provided with longitudinally extending elastic members for exerting an elastic contractive force between front and rear ends 105, 106. With the elastic contractive force, the leakage preventing wall 104 is raised from the skin-side surface between the front and rear ends 105, 106.
In the sanitary napkin 101, a front region 107a between the fold-back flaps 102, 102 is intended to face the vaginal opening, and an intermediate region 107b is intended to face the perineum and the anus. In a rear region 107c, the sanitary napkin is deformed to rise along the longitudinal centerline Oy-Oy for fit in the cleft of the buttocks.
Sanitary napkins of this type are disclosed, for example, in the following Patent Publications 1 and 2. In the sanitary napkin disclosed in the Patent Publication 1, since the rear ends 106, 106 of the leakage preventing walls 104, 104 are located farther rearward than shown in FIG. 8, menstrual blood discharged from the vaginal opening and trying to flow obliquely rearward may be blocked.
[Patent Publication 1]
    Japanese Unexamined Patent Publication No. 2001-95842[Patent Publication 2]    Japanese Unexamined Patent Publication No. H07-33314
When the undergarment is worn with the sanitary napkin 101 of FIG. 8 being adhered and fixed thereto, the inside of the wearer's thigh faces a region extending over a length of 150 to 170 mm with center at a transverse reference line Ox-Ox of the sanitary napkin 101. Since the thighs exert a transverse clamping force on this region, the leakage preventing walls 104, 104 come into contact with the thighs, hardly falling transversely outward.
Rearward of a line Lx-Lx that is spaced 70-80 mm apart rearwardly from the transverse reference line Ox-Ox, however, the leakage preventing walls 104, 104 cannot come into contact with the thighs. Rearward of the line Lx-Lx, moreover, the leakage preventing walls 104, 104 will be subjected to a pressure from the buttocks. Therefore, the leakage preventing walls 104, 104 rearward of the line Lx-Lx tend to fall outward without being constrained by the thighs.
In the conventional sanitary napkin 101 of FIG. 8, the rear flaps 103, 103 have side edges 103a, 103a that are located close to the leakage preventing walls 104, 104 on the line Lx-Lx. When the leakage preventing walls 104, 104 fall transversely outward, therefore, they extend beyond the side edges 103a, 103a, so that menstrual blood applied to the leakage preventing walls 104, 104 may possibly adhere to the undergarment outside the rear flaps 103, 103.
In the conventional sanitary napkin 101 of FIG. 8, furthermore, the side edges 103a, 103a of the rear flaps 103, 103 are gently inclined away from the longitudinal centerline Oy-Oy. Therefore, if menstrual blood flows out of the leakage preventing walls 104, 104 near the line Lx-Lx obliquely rearward as indicated by an arrow 109, the menstrual blood tends to leak out beyond the side edges 103a, 103a of the rear flaps 103, 103. This also results in leaving a stain on the undergarment.